Tolterodine (Xa), i.e. (R)-N,N-diisopropyl-3-(2-hydroxy-5-methylphenyl)-3-phenylpropanamine
is a medicament useful in the treatment of urinary incontinence. U.S. Pat. No. 5,382,600 and U.S. Pat. No. 5,922,914 disclose a method for the preparation of tolterodine, which is isolated in the last step by resolution of the previously obtained racemic mixture. Andersson, Pher G. et al., J. Org. Chem. 1998, 63, pp. 8067–8070 and U.S. Pat. No. 6,310,248 disclose an enantioselective synthesis of tolterodine, which allows to avoid enantiomers separation. The (S) enantiomer of tolterodine, i.e. (S)-N,N-diisopropyl-3-(2-hydroxy-5-methylphenyl)-3-phenylpropanamine (Xb)
and its use in therapy are disclosed in WO 98/03067. In particular, in U.S. Pat. No. 6,310,248 the key step in the synthesis of tolterodine and of its (S) enantiomer is the preparation of 6-methyl-4-(R)-phenyl-chroman-2-one (Ia)
and 6-methyl-4-(S)-phenyl-chroman-2-one (Ib)
in enantiomerically enriched form by means of enantioselective reactions.